The basic nature of the force, duration and frequency of tooth contacts during bruxing and mastication will be investigated. The changes in nocturnal bruxing habits with modification in occlusion will be measured. Time dependencies among jaw movement, EMG activity and tooth force will be documented. Forces recorded during bruxism will be compared with forces recorded during chewing to evaluate the potential damage to the periodontium of bruxism in relation to mastication. A system for measuring the jaw force has been developed as the first part of this project. This system deduces jaw force from variations in amplitude of introduced vibrations which are transmitted by the facial bones, periodontium, teeth and muscles. This system avoids using mouth appliances which could interfere with the preconscious jaw functions of chewing and bruxing. This vibration transmission system will be evaluated for use in measuring tooth mobility. The system appears useful in measuring muscle tension in limb muscles as well as jaw muscles.